Don't laugh. Just a name can dissuade half of the purchasing department
Two days ago, I met a customer and asked: How much is your corrugated compensator? As soon as I checked the drawings, boy, I asked for a metal expansion joint. Again: Are expansion joints and bellows the same thing? Yes, this problem happens a couple of times a week.
In fact, these three names — expansion joint, compensator, bellows — refer to the same thing, but they look at the problem from different angles. The metal expansion joint is called functionally: the pipe expands when heated, and it leaves a "joint" for expansion and contraction. Corrugated expansion joint is called structurally: the core piece is the stainless steel corrugated pipe, which absorbs displacement by corrugated deformation. As for metal hoses, they are close relatives, but they are not the same thing: hoses are mainly used to transport media plus flexible connections, and expansion joints are specially used to absorb displacement, so don't mix them.
Then why is it customary in the industry to call it "expansion joint" instead of "compensator"? Because the word "compensation" is too broad, sleeve compensator, spherical compensator and rotary compensator can be called, but only the metal expansion joint with bellows structure. Called expansion joint, it is equivalent to talking about half of the structure and principle first.
Structural naming: displacement code hidden in name
If you go through the names of the product lines in our station one by one, it is almost equivalent to reading half of the textbook of pipeline stress analysis. By what? Just look at the attributive in the naming.
For example, the general-purpose corrugated expansion joint, which is the most common single axial type, relies on the bellows to directly absorb the axial displacement of the thermal expansion and contraction of the tube. The guide tube and the tie rod are matched, and it's done.
Look at the double hinge transverse expansion joint again. What is "duplex"? Two bellows. What is "hinge"? Connect the two ends with a pin shaft, and the axial direction cannot move, but can only swing laterally. As soon as the name came out, the designer knew: Oh, this thing is mounted on L-shaped pipe sections, and it specializes in lateral displacement.
Straight pipe pressure balance expansion joint and curved pipe pressure balance expansion joint, the four words "pressure balance" in the name is the key-this thing is used to carry the blind plate force. If an ordinary expansion joint is installed on the straight pipe section, the internal pressure will generate a huge thrust to push the pipe away from the flange. The pressure balance type uses two bellows to offset this force, saving the main fixing bracket. You said, if you just look at the model number and not the name, who would have thought of this layer?
There are also external pressure single axial expansion joints. "External pressure" means that the bellows bears external pressure, and the medium goes between the outer pipe and the bellows. This structure has good stability and is suitable for large-diameter and high-pressure steam pipelines. Every word in a name is a message, and none can be saved.
Industry Naming: Suffix is the Statement of Work
The same expansion joint changed a business card when it came to different industries. Our station has corrugated expansion joints for power station industry and metal corrugated expansion joints for cement industry. The suffix is not hung casually.
What is the difference between power station, desulfurization and cement? Temperature, dust, corrosion, life requirements are all different. For expansion joints used in cement industry, bellows must consider wear resistance, and the guide tube must be thickened, otherwise the clinker dust will wear the bellows out a few times. The expansion joint of the desulfurization system has sulfur in the medium and low acid dew point. The material has to be 316L or even higher corrosion-resistant alloy, and the external skin and internal insulation layer have to be redesigned.
So when you see the word "power station", what pops out of your mind is not the power plant gate, but high-temperature and high-pressure steam, frequent start-and-stop, and the need for low-stiffness design scheme-this is called doorway.
Naming of shape and function: rectangular, non-metallic, directly buried, each with its own origin
The metal rectangular expansion joint is for the smoke air duct. The air duct is of square section, so you can't force a round pipe into it. Circular expansion joints correspond to circular pipes, such as fan inlet and outlet. As for the large-diameter thick-walled expansion joint, the name has already shouted out the core selling point: large diameter and thick wall, specially dealing with high-pressure or large-size pipelines, and the manufacturing threshold is not generally high.
The directly buried (fully buried) expansion joint is more straightforward, that is, it is buried in the soil, and there is no inspection well. This name tells the construction party: bury it directly, don't build a well, save space and money. But the premise is that the outside of the bellows has to be tightly sheathed, otherwise the groundwater will be finished as soon as it soaks.
Then why do non-metallic expansion joints (fabric fiber expansion joints) and rubber compensators have to emphasize "non-metallic" and "rubber" in their names? Because that material determine the application boundary. Non-metal can withstand large displacement, low pressure, good heat insulation, suitable for flue gas, hot air and other hot and not much pressure occasions; The rubber compensator is acid and alkali resistant, cheap, and suitable for low-pressure liquid pipelines such as water supply and sewage. They are not called "metal expansion joints", because they are afraid that if you buy them back and use them in the wrong place, who belongs to an accident?
Key points of identification under chaos
Is the name messy or not? Chaos. Some people in the market call it corrugated compensator, some call it expansion joint, and some people put the sleeve-type pipe expansion joint into the expansion joint-the sleeve does depend on expansion compensation, but it has no bellows, and is realized by packing seal sliding. The design logic and fatigue life are completely another system. You can say that it is an expansion joint, but if you want to set the structural parameters according to the corrugated expansion joint, you will have to stumble.
Then how to judge the substance of the product from the name in purchasing or design? Three tricks: take a look at the core structure and see if there are three words "bellows" in the name; Second, look at the displacement mode, axial, transverse and angular, and there are generally tips in the name; Third, look at the application scenario, and the industry suffix directly benchmarks the working conditions. If the model name found on the Internet does not match your actual needs, don't rush to place an order, send the working condition parameters to the supplier, and let them help you confirm it.
In the final analysis, the naming of metal expansion joints is not literary, and it is not a bunch of attributes for manufacturers to appear professional. Behind each adjective are design constraints and working condition requirements. Understand this set of naming logic, whether you are looking at the catalog or running the scene, you have a bottom in your heart.
The name seemed to be a trivial matter, but only those who had actually had an accident knew its weight.